With a new year come changes in tax limits—and 2012 is no exception. Bush tax cuts will expire at the end of this year, so that will force Congress's hand to make some changes. Here are four new tax limits to watch out for:

1. MILEAGE RATES

When you use your personal vehicle for your own medical visits, travel to and from your physician's office is deductible as part of a medical expense deduction, as long as these espenses in total exceed 7.5 percent of your adjusted gross income. The mileage allowance is 23 cents per mile. Auto mileage for the purpose of computing a charitable deduction is 14 cents per mile, and the allowance for business auto use is 55.5 cents per mile. Keep in mind that you always have the option of calculating the actual costs of using your vehicle rather than using the standard mileage rates.

However, you can't use the business standard mileage rate for a vehicle after using any depreciation method under the Modified Accelerated Cost Recovery System (MACRS) or after claiming a Section 179 deduction for that vehicle. In addition, you can't use the business standard mileage rate for more than four vehicles simultaneously.

2. RETIREMENT CONTRIBUTIONS

The maximum contribution limits for 401(k) plans for employee deferrals have increased from $500 to $17,000 and if you're over the age of 50, the limit now stands at $22,500. Review your contribution deferrals and adjust them if you want to take advantage of the maximum amount. The limits for SIMPLE plans for employee deferrals did not change and stand at $11,500 if you're under the age of 50 and at $14,000 if you're over the age of 50. Even if you're not contributing the maximum, if your employer offers any type of retirement plan, you should participate up to the amount that your employer will match. This is typically 3 percent to 4 percent of your yearly earnings. With the help of your employer and the investing power of compounding, you'll be much farther along in reaching your retirement objective than if you don't participate. The younger you start, the farther along you will be.

3. HEALTH SAVINGS ACCOUNTS

The limits for contributions to health savings accounts for 2012 are at $3,100 for self-only coverage and $6,250 for family coverage. Catch-up contributions for those 55 and older remain at $1,000.

4. HEALTH INSURANCE CREDITS

Practices can still benefit from tax credits as incentives to provide health insurance coverage. Employers with 10 or fewer employees and average annual wages of less than $25,000 can receive a credit of up to 35 percent of their health premium costs each year through 2013. The credit is phased out for practices larger than that and disappears completely if a company has more than 25 employees or average annual wages of $50,000 or more. Beginning in 2014, small veterinary practices that sign up with one of the health exchanges to be created can receive a credit of up to 50 percent of their costs.

Unless things change this year, massive tax increases that were passed with the Obama healthcare tax legislation back in 2010 will go into effect January 1, 2013. Many people have forgotten these changes were passed, but we're now less than one year from seeing them implemented. Starting in 2013, a 0.9 percent Medicare surtax will apply to wages in excess of $200,000 for single taxpayers and more than $250,000 for married couples.

Also, for the first time, a Medicare tax will apply to investment income of high earners. The 3.8 percent levy will hit the lesser of their unearned income or the amount by which their adjusted gross income exceeds the $200,000 or $250,000 threshold amounts. The new law defines unearned income as interest, dividends, capital gains, annuities, royalties, and rents. Tax-exempt interest won't be included, nor will income from retirement accounts. Make sure you do your research and stay current so you can take advantage of these limits.